FiiO K13 R2R silver

The K13 R2R marks the evolution of the K11 R2R in the FiiO lineup. This desktop DAC and headphone amplifier is built around a proprietary 192-resistor R2R converter, balanced amplification delivering 2400 mW per channel, and extensive connectivity including LDAC Bluetooth, balanced XLR outputs, and a 10-band parametric equalizer. Designed to drive both sensitive IEMs and demanding planar headphones, it positions itself as a complete desktop solution with two distinct conversion modes (NOS and OS) and dual DC/AC power supply.

The beating heart: a proprietary 192-resistor R2R DAC

At the center of the K13 R2R lies a converter developed by FiiO, built around a fully differential four-channel R2R (resistor-to-resistor) topology. This approach differs from the delta-sigma circuits that dominate the market. While a delta-sigma DAC oversamples the signal at very high frequencies before decoding it, the R2R directly converts each PCM sample into analog voltage through a network of calibrated resistors.

The circuit integrates 48 thin-film resistors per channel, totaling 192 components. Each resistor displays ±0.1% precision and thermal drift limited to 30 ppm. FiiO’s proprietary error correction algorithm compensates for inevitable imperfections to achieve performance compatible with 32-bit/384 kHz high definition.

The differential configuration means each channel uses two resistor networks in phase opposition. This symmetry reduces parasitic harmonics and improves common-mode noise rejection, resulting in a lower noise floor and minimal crosstalk between channels. Native DSD decoding up to DSD256 is performed in direct 1-bit mode, without intermediate conversion to PCM. For PCM streams, the K13 R2R accepts up to 384 kHz at 32 bits via USB, and up to 192 kHz on coaxial and optical inputs.

Two sonic philosophies: NOS and OS modes

The K13 R2R offers two operating modes. NOS (Non-Oversampling) mode maintains the signal at its original sampling frequency. A CD at 44.1 kHz remains at 44.1 kHz, preserving the original waveform without interpolation. OS (Oversampling) mode upsamples all signals to 384 kHz before conversion, enabling sharper digital filtering with generally superior technical metrics.

Switching between NOS and OS is done via the menu, accessible from the volume knob. This flexibility allows adapting the rendering to the source, the headphones used, and personal preferences. DSD files are always decoded natively, regardless of the selected mode.

Uncompromising amplification power

The amplification stage delivers 2400 mW + 2400 mW into 32 Ω on the 4.4 mm balanced output, and 600 mW on the 6.35 mm single-ended output. This power enables driving high-impedance headphones like magnetic planars, while maintaining the finesse necessary for ultra-sensitive IEMs thanks to three independent gain levels.

Each gain level has its own volume curve, adapting the potentiometer progression to the sensitivity of the connected transducer. The fully balanced amplification chain, from DAC to headphone output, ensures better electromagnetic interference rejection and greater dynamic headroom. Integrated protections against thermal overload and switching noise preserve driver integrity.

The 10-band parametric equalizer powered by XMOS XU316

The K13 R2R integrates a 10-band parametric equalizer, an unusual feature on a desktop DAC at this price point. Processing is handled by the XMOS XU316 platform, a multi-core controller offering 16 logical cores and up to 2400 MIPS of deterministic computing power. The XU316 simultaneously manages the USB 2.0 high-speed interface, audio decoding, and real-time equalization calculations.

Equalization operates up to 192 kHz / 24 bits and remains active regardless of conversion mode or selected input. Access is via the FiiO Control smartphone app, or through a web interface in USB mode. Each band has three adjustable parameters: center frequency, gain, and bandwidth. The app offers presets and an Auto-EQ function capable of importing measurement profiles to automatically generate a compensation curve. Settings can be saved, exported, and imported, allowing configuration sharing or quick switching between multiple headphones.

“Skylight” design and uncompromising construction

The machined monoblock aluminum chassis adopts the minimalist language of the K11 series, with a remarkable innovation: a circular glass window on top revealing the R2R resistor networks. Customizable RGB lighting surrounds this window, with static, dynamic, or sampling frequency-synchronized modes. Brightness is adjustable across multiple levels or can be turned off completely.

The high-definition, high-contrast LCD display occupies the front panel. Unlike OLED screens prone to burn-in, this panel can remain on permanently without degradation. It simultaneously displays sampling frequency, volume, gain level, output mode, and selected input.

Two knurled anodized aluminum knobs control the unit: the larger one manages volume, the second navigates between inputs and settings. This approach avoids deep menus and complex manipulations. An infrared remote control also enables remote operation. The anti-slip feet have been redesigned with four adhesive rubber feet that firmly hold the unit in place, unlike the slippery pad of the K11 R2R.

Complete connectivity: from wireless to balanced

The rear panel features three wired digital inputs: USB-C (up to 384 kHz / 32-bit PCM and native DSD256), Toslink optical, and RCA coaxial (up to 192 kHz / 24 bits). USB uses asynchronous transmission to minimize jitter. Bluetooth 5.4 adds a wireless option with support for LDAC codecs (up to 990 kbps), AAC, and SBC.

Audio outputs are divided into two categories. For headphones: 6.35 mm single-ended jack and 4.4 mm Pentaconn balanced on the front panel. For preamp use: single-ended RCA and balanced XLR at the rear, operating in fixed or variable level. Volume memories remain independent between headphone output and preamp output.

Dual DC/AC power supply and expansion capability

The K13 R2R features a 30 W switching power supply shielded by a nickel-plated alloy cover. Internally, 18 low-noise linear regulators and 5 DC-DC converters distribute power to different circuit sections. This multi-rail architecture isolates each function to limit mutual interference. Filter capacitors include ELNA RA3, a series designed for audio applications, and tantalum capacitors.

A 12 V DC input allows connecting an external linear power supply (minimum 2.5 A) for those wishing to explore the influence of different power supplies on sound rendering. When an external power supply is connected, the K13 R2R automatically switches to it and disables the internal power supply.

Technical Specifications

Digital-to-Analog Conversion

• DAC type: fully differential 24-bit R2R resistive, 4 channels
• Internal architecture: 48 precision resistors per channel, 192 resistors in total
• Resistor precision: ±0.1%, low thermal drift of 30 ppm
• Symmetrical conversion: reduced noise and harmonics for a silent background
• Available conversion modes:
  • NOS (no oversampling): natural signal reproduction without processing
  • OS (oversampling): processing up to 384 kHz for enhanced accuracy
• Audio format compatibility: PCM up to 384 kHz / 32-bit, native DSD256

Amplification and Power

• Amplification architecture: fully balanced, from the DAC to the headphone output
• Output power: 2400 mW + 2400 mW at 32 Ω on balanced output
• Gain control: 3 independent gain levels with custom volume curves
• Built-in protections: against overheating, overload, and power on/off switching noise

Audio Processing and Equalization

• Built-in 10-band parametric EQ: precise adjustments up to 192 kHz / 24-bit
• Access and control: via the FiiO Control app or web interface
• Advanced features: import/export settings, sharing, and automatic headphone response correction
• Preamplifier / power amplifier mode: dedicated RCA and balanced outputs
• Independent memory: separate volumes for headphone out and preamp modes

Connectivity and Interfaces

• Digital inputs: USB, optical, coaxial
• Wireless connectivity: Bluetooth 5.4 with LDAC, AAC, SBC codecs
• Audio outputs:
  • 4.4 mm balanced headphone
  • 6.35 mm single-ended headphone
  • RCA preamp
• Control methods: dual knob, infrared remote, FiiO Control app

Power Supply

• Internal power supply: 30 W shielded switching supply with nickel-plated alloy
• External power compatibility: 12 V / 2.5 A minimum linear supply, 5.5 × 2.1 mm connector
• Voltage regulation: 18 low-noise linear regulators and 5 DC-DC converters
• Capacitors: ELNA RA3 and high-quality audio tantalum capacitors

Construction and Design

• Chassis: unibody machined aluminum with anodized finish
• Display: high-definition, high-contrast LCD with no burn-in risk
• Customizable RGB lighting: sample rate indicator, brightness setting, and breathing effect
• Auto power-off timer: adjustable from 1 to 99 minutes

Box Contents

• FiiO K13 R2R
• Infrared remote control
• Power cable
• USB cable
• Headphone adapter
• Quick start guide
• Warranty card

Specifications Summary

• DAC: 4-channel 24-bit R2R
• Resistors: 192 in total, 48 per channel
• PCM format: up to 384 kHz / 32-bit
• DSD format: native DSD256
• Balanced output power: 2400 mW + 2400 mW at 32 Ω
• External power: 12 V / 2.5 A minimum
• Wireless connectivity: Bluetooth 5.4 with LDAC, AAC, SBC codecs